Olin Lathrop wrote:
> N. T. wrote:
>> 20ma/5V lamp is 250 Ohm at 20ma and I expect it to be less than 20 Ohm
>> when cold. It should be quite linear at small AC signals, say less
>> than 100 mV. Feed the lamp with a constant current source regulated by
>> a microcontroller.
>
> That is basically Bill Hewlett's design for gain control of his oscillato=
r.

It is, I think,
http://www.google.com/patents?id=3DtW5jAAAAEBAJ&printsec=3Ddrawing&zoom=3D4=
#v=3Donepage&q&f=3Dfalse
--=20
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